That looks like powdery mildew. If you can get some potassium bicarbonate to mix with water and spray on the plants it could help.
How strong a solution. I have it on my eggplants and often get it on my cucumbers. I would like to save the plants if possible
Thanks TCLynx I'll try a solution tomorrow.
I've seen things that say 4 teaspoons up to 2 tablespoons of potassium bicarbonate or even baking soda per gallon of water mixed up and sprayed on the plants. I prefer the potassium bicarbonate since it will provide potassium at the same time as changing the leaf surface pH. Changing the leaf surface pH can help combat fungus and powdery mildew tends to attack plants suffering from potassium deficiency. At least that is what I've been told, I've not actually studied horticulture in school or anything.
I have used this in the past for powdery mildew
Mix 1/4 teaspoon(1.25ml) of Baking Soda with 3/4 teaspoon(3.75ml) of Epsom salt in 1 litre ( 4 cups) water. Mix solution well. I like to use room temp water for the solution, nothing too cold
Foliar spray the plants liberally. Wash off after one or two days by misting with water. The solution may leave a white haze on the leaves of the plants, which will eventually wash off. I didn't have haze of any consequence when I used this solution.
I have been fighting mildew myself, I have tried neem, to fix it did not work for me.
I have been told that skim milk works good for treating this, I plan on trying this coming summer.